Trepidation & Armistice
by BiOriX
Summary: My take on the entire story of UNDERTALE (backstory, game itself, chapter of aftermath). Will include canon elements, with a few of my own ideas mixed in.
1. Prologue

Prologue – _Monsters_

Monsters. When you hear of monsters, you most likely just think of legend, or fable. However, this was not always the case. Not too long ago, monsters lived alongside and co-ruled the world with the humans. The humans did not think very much of them, though, as they were weaker by a load, but they tolerated them.

Yet, one day, for some unknown reason, war broke out between the two ruling species, and the humans fated victorious, banishing the remaining monsters to the Underground, sealed by a magical barrier.

The monsters were broken and dishevelled; they were torn with despair. The monster king, King Asgore Dreemurr, attempted to calm them, and it just barely worked—their forced tranquillity still hung by a thread. The king and his wife cast a spell over themselves: a spell that would halt their ageing—they didn't know if the monsters could go on without them, and they were getting older. But, if they were to be honest: they had no clue of what to do themselves.

But finally, the king goat (Asgore) hatched a plan. A plan to exit the barrier and destroy the humans in vengeance. But for that, he needed a scientist. The king called out for applicants—and he found a very eager one, at that. A skeleton in his early 20s, Dr WD Gaster, jumped at the chance to make an impact and get some recognition. He was brilliant but unnoticed, and craved some attention. He knew nearly everything about everything! After proving his smarts to the king, he was hired as the very first Royal Scientist of the Underground.

Gaster was tasked (along with some extra, smaller things) with extracting a substance found only in humans, and injecting it into monsters. This substance was known as Determination—the will to keep living. The strength of the humans. The power of Determination was why human Souls would still linger with their owner's consciousness after death—monster Souls perished instantaneously.

How were they to extract Determination from humans when there were none to be found? Gaster needn't even ponder over this thought for a second—he had an idea: he would create a human substitute. How, you may ask? With water. Water is the most essential element to a human's survival—without it, they'd die before half a week passed. With the monsters' limited knowledge of the human body, this seemed like a perfect idea. He would extract a little bit of himself (since he was a skeleton it wouldn't hurt) and keep it contained in a large tube filled to the brim with clairvoyant water. He would recreate a humanoid substitute. After setting up his experiment, Gaster set off to sleep.

Chapter 1— _Unexpected Company_

Gaster was already at his lab when he fully woke up—he seemed to have sleepwalked his way to work. With a start, he eagerly yet slowly walked toward his experiment room. Opening the door, he was taken aback to see two new skeletons staring at each other through the glass. Not only had the scientist not expected new life so early—though he was proud that it had worked—but it also meant his idea failed. At least, he thought so, at first. He slowly went to go release the skeletal bodies from their prison; the taller one hopped out 'heroically', holding his fist in the air, while the shorter one just casually stepped out.

"heya," greeted the short one. "i'm sans. this is my (i think) brother, papyrus."

"GREETINGS, CREATOR," spoke the tall one confidently. "I, THE GREAT PAPYRUS, AM GLAD TO MEET YOU! MAY I INTEREST YOU IN STORIES OF HOW GREAT I AM?"

"Uh, no, thank you," replied Dr Gaster. "I'm good for now." Gaster still planned to test on them—but these introductions already made him feel sick to do so. There was something about the few words they said that made him like them both a lot. He felt terrible even thinking about slicing them up to even just _see_ if they had Determination in them.

There was an awkward silence. "WELL!" Papyrus clapped his hands together. "I THINK, TO BREAK THE SILENCE, I SHOULD TELL MY STORIES! IT ALL STARTED, LONG AGO—"

"bro, you were literally created twenty seconds ago." interrupted Sans. "besides, i'm a humour kinda guy, and i doubt your stories would be very ... _humerus_ ," he joked. Gaster snickered uncontrollably; Papyrus cringed.

"SANS!" whined Papyrus. "NOW IS NOT THE TIME FOR JOKES!"

"then when will it be time, pap?" grinned Sans. "WHEN NO ONE ELSE IS AROUND!"

"aw..." Papyrus' brother fake-whined. "but then i'll be all ... a- _bone,_ " Gaster made a poor excuse for attempting to hold in his laughter; Papyrus' yell of rage was heard from miles away. "Come on, Papyrus, you gotta admit that was good." Gaster breathed in between howls of laughter. He liked these guys—even if Papyrus would refuse to co-operate. But the scientist's laughs were cut short when he remembered his task at hand: kill them, open them, find Determination and take it. His smile faltered immediately and he felt sick. He couldn't do it. But how else would he find Determination?

"SANS!" Papyrus yelled, trying to hold in his grin. "THAT WASN'T FUNNY!"

"then why are you grinning?" Sans chuckled.

"I AM AND I HATE IT!"

They all three began to laugh, Gaster just barely. He needed a plan ... a good plan, one that would work for sure ... and it hit him. He didn't necessarily like it, but it was for the best. For the first time in his life, he was going to procrastinate, and wait until a better opportunity presents itself to him. Instead of using his smarts for his biggest and apparently most important task, he was merely going to work on other small projects he was tasked with and would wait for a human to arrive. _These extra projects are to be finished_ after _Project Determination_ , the scientist remembered king Asgore saying. But he couldn't bring himself to kill these guys. He had to wait.

A/N: I had originally written Sans and Papyrus' lines in their respective fonts, but I guess FF doesn't like that. Sorry! ^_^ Hope you're enjoying this so far. I know this isn't actual _fan_ fiction, but for the longest time, I've wanted to write down the amazing story and share it, so sorry if it bothers you to see _fiction_ on a _fan_ fiction website. I'll (try to) update this frequently!


	2. Blueprints

Chapter 2— _Blueprints_

The three skeletons bonded over these horrible jokes (with the occasional groans and yells coming from Sans' brother) for what seemed like an hour, before 'the great' Papyrus whined, in his most childish voice possible, "I'M TIRED! SANS, CAN YOU READ ME A BEDTIME STORY?" Sans wore his never-faltering grin with what would be a blank stare on his face.

"..." Sans stood still. "there's no bed or books, papyrus. and it's only something o'clock."

"BUT SANS!" Papyrus whined loudly again. "I'M TIRED!" Papyrus was nearly yelling at this point.

"ok, let's go," Sans spoke quickly, slightly pushing his brother forward, and Papyrus kept walking. "hey, gas, you got any books i could read to him or something?"

"Don't," Gaster started just before the short skeleton finished his sentence. "call me Gas ... just don't."

"alright, i'll try again." Sans stepped backwards, retook another step _forward,_ and spoke again. "hey, gast, you got any books i can read to him?"

"SANS!"

"just a minute, pap."

"I ... fine, I guess ... Gast is better," Gaster gave in, annoyed, as he began rummaging through his massive bookshelf. "Um ... I do have, uh ... this ... quantum physics book?"

"eh, i guess it'll do," Sans shrugged, grasping the book and walking back towards Papyrus. "see ya."

And just like that, Dr Gaster was left alone for the night. He thought to himself of the jokes that Sans had shared, but his amusement was cut short by the thoughts of the consequences there would be once Asgore found out that he'd delayed _Project Determination_ creeping into his mind, but he had to force those ideas out of his head. Instead, he thought of the other big projects he'd been tasked with. He remembered immediately the project he had been most looking forward to: construct a path or passageway from Hotland to New Home.

Gaster had always been fascinated with construction – and he's built many times before – and the Underground really was in need of a less dangerous way to traverse back and forth between the two areas than having to jump across hundreds of platforms of dark rock, with the intimidating lava glowing red beneath. Many people lost their lives just attempting to get to the King from Hotland, even if it was just to deliver a pizza. Eager to get started, the skeleton threw open his second-lowest drawer below his black desk and grabbed a few sheets of blueprint.

He had no plans – he just began doodling rough sketches of very fascinating and imaginative buildings until he created something that he knew would truly impress King Asgore. Every drawing he made seemed too complex or just impossible … but it couldn't be too simple, or else Gaster might lose his job! Gaster could tell by the King's amazement when he proved himself that Asgore expected a lot from him – something cool and genius – but Gaster also wanted to impress himself.

The Royal Scientist continued to sketch for a few more minutes, before a sudden voice rang beside him.

"heya."

Gaster shouted in terror and darted his head to glance to his left – it was just Sans. The scientist recomposed himself quickly and crumpled up the blueprint he had been etching on and threw it in the garbage bin. He sighed.

"Hi. Is Papyrus sleeping?"

"yeah, but it was a real pain though. that quantum physics book you gave me? It had a joke book inside. i look inside the joke book, and there was another quantum physics book. i repeated this process a few times, before i just grasped the book by the spine and shook it. there were probably at least fifty books of that caliber in there that just tumbled out. me, being the amazing person i am, picked them all up and arranged them back in the original order. by the time that finished, papyrus was already asleep. so here i am." There was a long pause. "can i keep it?"

Gaster chuckled slightly. "Sure, knock yourself out." He grabbed another blue sheet and began his random delineations yet again. He began with the four support columns for each corner and continued with the rest of the rectangular form. He added arcs and tubes for decoration – many spheres were added in a satisfying manner. This one was coming along nicely.

"whatcha workin' on?" Sans asked, peering over Gaster's shoulder and scanning the ocean blue-coloured paper.

"Oh, just a project the King wanted me to work on, nothing special," Gaster replied nonchalantly. "Why?"

"looks good, dude."

"Thanks," Gaster smiled. "What do you think I should call it?" He added, as he put the finishing lines and dots for architectural support and nice looks.

"well, what is it and what's its purpose?"

"It's a passageway from Hotland to New Home – the current one is way too dangerous – over 26% of the Underground population was lost trying to get to or from New Home. It's basically … well, just a passageway."

Sans stared at him. "really? you're putting' all this work into a _passageway_? looking at it, i'd assume it was something technologically advanced, maybe the core of the underground's power or something … i mean, the underground is so low on tech and very outdated–"

"Oh my god, that's _GENIUS_!" Gaster exclaimed, beaming. "Sans, you're a genius! Wow – wait, how do you know about the technology of the Underground?"

"do you not get it?" Sans asked, scoffing. "papyrus and I … we're parts of you. We have your different personality traits, we're angered, saddened, overjoyed, all by the same things, we have your memories and all. i'm your smart and intelligent side that _really_ loves bad jokes, Papyrus is your craving for recognition, your tendency to overthink things, your perfectionism, all of it. i know about the technology because i have your memories."

"Wait," Gaster was attempting to digest the information. "so that genius idea, then … that was me?"

"exactly. and papyrus whining that he was really sleepy–"

"Oh God," Gaster scoffed. "that was me too?"

"yep."

"Wait," Gaster was stuttering a bit. "If I … if I died, would you two …?"

"nah, we'd live still," Sans shrugged the idea away. "but don't go out and about dying now."

"Yeah, okay, I'll try not to die," Gaster laughed. "So, do you know exactly what I'm gonna say next?"

"c'mon now, we're not psychic," Sans spoke. "as soon as we were created, we began creating our own memories, too. we're still people, gast."

Gaster stretched. "Yeah, that makes sense." A great big sigh. "So, technologically advanced core of the Underground, huh? What should we call it? I'm thinking something truly awesome-sounding, like … Zentrum … or Mittelpunkt, maybe. Those are words for core in German–"

"why not just, 'core'?" Sans suggested. "much easier, and still sounds cool, doesn't it?"

"Oh …" Gaster spoke. "Yeah, haha." He took his pencil and wrote, in big, bold letters, ' _ **CORE**_ '. And the blueprint was done. "I'm really proud of this one, actually!"

"yeah, nice job," Sans pat Gaster on the back.

"I think I'm gonna go show Asgore right now, he's gonna be so proud!" And he zoomed off.

"wait!" Sans called out. "that's probably not a good … idea." But Gaster was already gone.

 **A/N: Almost a month! Wow, this took a while to finish. But I think it was worth it – this chapter is really good, in my opinion. I do understand at some parts it may seem a bit rushed, and that's totally true in some spots, but I just really,** _ **really**_ **wanted to get this finished tonight. The next two chapters will be focusing on the most important backstory, so stay tuned … ;)**


End file.
